This invention relates to a support linkage for supporting a header on a support frame of a crop harvesting machine.
The present invention is particularly but not exclusively designed for use with swathers, which may be of the self propelled or pulled variety.
Self propelled swathers generally comprise a tractor unit which has a frame carried by a pair of driven front wheels which straddle the swath and hence are positioned at respective sides of the driver platform so as to extend downwardly therefrom. Conventionally the wheels are driven by hydraulic motors mounted at a lower end of the wheel support struts. The rear wheels supporting the frame are generally castor wheels which are positioned at the rear of the platform and again spaced widely to straddle the swath. Pull-type swathers include a frame mounted on a pair of spaced ground wheels with the frame attached to a hitch pole for connection to a separate tractor unit.
In both cases the frame is designed to accomodate different headers which can vary significantly in width and weight depending upon the crop and depending upon the land conditions. It is necessary therefore for the swather frame to be designed to accomodate headers of significantly different weight and to allow adjustment of the cutting height of the header. Furthermore the header must be mounted so that it can float, that is it can fall to a required cutting height but can lift away from that height if it comes into engagement with the ground or with any other obstacle to prevent damage. In addition the header must be raisable under control of the operator so that it can be raised from certain obstacles and so that it can be lifted away from the ground for transportation when inoperative.
Various designs of support linkage have previously been proposed for holding the header relative to the frame in a manner which accomodates the above requirements. Generally the linkage includes left and right linkages each seperately connected to the frame. Generally each support linkage comprises a top link, a bottom link and a float spring arrangement which tends to lift the header around the pivotal links from a lower stop position to enable the header to float away from contact with any obstacle on the ground. One example of the prior art is described hereinafter.
However the designs previously put forward have had a number of limitations and disadvantages and it is one object of the present invention to provide an improved design of support linkage of this general type.